evas + gl - fix callback-to-app-changes-state issue with pixel data
so if we call a callback that has e do something like set new pixel
data in a pixel data provider and we do it from the is pixel inside
call ebcause pixels were marked as dirty - pixels may no longer exist
after that, so re-get to make sure and handle properly.
this was found with tiling + e + shaped windows + moving them around
in tiling. it's a valid efl bug though.